can sith use lightsabers?

In the new trailer there is a brief clip of senator palpatine wileding a lightsaber - looking like the sith emperor. According to a colleague the sith should not be able to use a ligfhtsaber is this true?

There are a couple problems with this post. First of all there needs to say in the Title *spoilers* so you can warn people that their is EIII stuff in the post. Second this should be discussed in 3SA